1. Field of the Invention
This invention relates to integrated circuits, and in particular, to a method of protecting an integrated circuit from radiation by fabricating a layer of radiation resistant material over the surface of the integrated circuit structure at the same time leads are attached to the integrated circuit.
2. Description of the Prior Art
Tape automated bonding of leads to integrated circuits is well known. Tape automated bonding provides a technique for interconnecting leads to integrated circuits by fabricating the leads on a continuous film support. The film is usually a plastic material along the edges of which sprocket holes have been formed to enable advancement of the film support and leads in automated bonding equipment. Typically, the leads are formed by depositing a thin film of copper or other electrically conductive material on the surface of the plastic. This conductive material is then etched to create the desired pattern of leads.
In the prior art, each pattern of leads has associated with it a central window or opening, termed a "personality window," in the continuous film support plastic or other material. The conductive leads are cantilevered over the edge of the supporting structure into the personality window, and are bonded to the integrated circuit die. Integrated circuits used in conjunction with such a technique include a raised portion of electrically conductive material known as a "bump" wherever a lead is to be attached. The leads on the plastic substrate are bonded to the bumps using well known processes, for example, reflow solder or thermal compression.
Also known is a technique for protecting an integrated circuit from incident radiation by covering the upper surface of the integrated circuit with liquid plastic of a radiation resistant type. The integrated circuit with liquid plastic is then heated to cure the liquid plastic. Unfortunately, such an operation requires an extra production step and causes a diminished yield of acceptable quality products because shrinkage of the plastic often destroys the bonds made between the leads and the die.